Booleans and nil

Coin Quest needs to know whether a door is unlocked and whether the player has selected an item. Those are states, not messages.

A boolean is a two-state value: true or false. It is useful for facts that can be answered yes or no.

nil means a value is absent. The strings "true" and "nil" are ordinary text and do not carry those meanings.

Read selectedItem: string? as selectedItem may hold text or no value. The colon introduces a type note and the question mark allows nil. The = nil after it supplies the current value. This small preview lets the strict editor accept an item that starts empty and later receives text.

--!strict asks Studio to check your code for type mistakes. It is an instruction for the editor and produces no Output message.

print(...) calls the built-in print function. Put the values to show inside its parentheses; separate multiple values with commas. Read the result in Studio's Output panel.

local is read as “local”: it creates a name that is available only in the current code scope.

A colon in a declaration, such as coins: number, introduces a type annotation: the kind of value that name is allowed to hold.

? is read as “optional”: it marks a type that may also be nil.

= is read as “is assigned”: it evaluates the right side and stores that value in the name on the left.

Read one statement at a time: name the value being read, what the operation does, and where its result goes. Keep identifiers exactly as written so you can find them again in the code.

Pause at calls, conditions, and loops. Explain when the body runs before moving to the next statement; use the line notes above when a symbol is unfamiliar.

Begin at the first executable statement. Comments and blank lines do not run; a branch chooses which block runs, and a loop may revisit its body.

Line 3: false is a boolean representing the locked state.

Line 4: The question mark allows the string variable to have no value; nil supplies that absence.

Line 6: Both current states are printed for inspection.

Before running, identify the starting values and any existing Studio objects this example needs. List what you expect to change.

After your practice change, check this result: The state variables change type-safely from locked to unlocked and absent item to named item.

Reading or printing a value leaves it unchanged. Look for assignments, calls that change state, and property updates to explain each change you observe.